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[InstCombine] Fold operation into select, when one operand is zext of select's condition #166816

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Merged
merged 1 commit into from
Nov 8, 2025
+9 −23
Merged

[InstCombine] Fold operation into select, when one operand is zext of select's condition #166816

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3 changes: 3 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1758,6 +1758,9 @@ static Value *simplifyOperationIntoSelectOperand(Instruction &I, SelectInst *SI,
m_Specific(Op), m_Value(V))) &&
isGuaranteedNotToBeUndefOrPoison(V)) {
// Pass
} else if (match(Op, m_ZExt(m_Specific(SI->getCondition())))) {
V = IsTrueArm ? ConstantInt::get(Op->getType(), 1)
: ConstantInt::getNullValue(Op->getType());
} else {
V = Op;
}
Expand Down
29 changes: 6 additions & 23 deletions llvm/test/Transforms/InstCombine/binop-select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -406,10 +406,7 @@ define i32 @ashr_sel_op1_use(i1 %b) {

define i8 @commonArgWithOr0(i1 %arg0) {
; CHECK-LABEL: @commonArgWithOr0(
; CHECK-NEXT: [[V0:%.*]] = zext i1 [[ARG0:%.*]] to i8
; CHECK-NEXT: [[V1:%.*]] = select i1 [[ARG0]], i8 0, i8 8
; CHECK-NEXT: [[V2:%.*]] = or disjoint i8 [[V1]], [[V0]]
; CHECK-NEXT: [[V3:%.*]] = or disjoint i8 [[V2]], 16
; CHECK-NEXT: [[V3:%.*]] = select i1 [[ARG0:%.*]], i8 17, i8 24
; CHECK-NEXT: ret i8 [[V3]]
;
%v0 = zext i1 %arg0 to i8
Expand All @@ -433,10 +430,7 @@ define i8 @commonArgWithOr1(i1 %arg0) {

define i8 @commonArgWithOr2(i1 %arg0) {
; CHECK-LABEL: @commonArgWithOr2(
; CHECK-NEXT: [[V0:%.*]] = zext i1 [[ARG0:%.*]] to i8
; CHECK-NEXT: [[V1:%.*]] = select i1 [[ARG0]], i8 5, i8 42
; CHECK-NEXT: [[V2:%.*]] = or i8 [[V1]], [[V0]]
; CHECK-NEXT: [[V3:%.*]] = or disjoint i8 [[V2]], 16
; CHECK-NEXT: [[V3:%.*]] = select i1 [[ARG0:%.*]], i8 21, i8 58
; CHECK-NEXT: ret i8 [[V3]]
;
%v0 = zext i1 %arg0 to i8
Expand Down Expand Up @@ -496,10 +490,7 @@ define i8 @commonArgWithAnd3(i1 %arg0) {

define i8 @commonArgWithXor0(i1 %arg0) {
; CHECK-LABEL: @commonArgWithXor0(
; CHECK-NEXT: [[V0:%.*]] = zext i1 [[ARG0:%.*]] to i8
; CHECK-NEXT: [[V1:%.*]] = select i1 [[ARG0]], i8 0, i8 8
; CHECK-NEXT: [[V2:%.*]] = or disjoint i8 [[V1]], [[V0]]
; CHECK-NEXT: [[V3:%.*]] = or disjoint i8 [[V2]], 16
; CHECK-NEXT: [[V3:%.*]] = select i1 [[ARG0:%.*]], i8 17, i8 24
; CHECK-NEXT: ret i8 [[V3]]
;
%v0 = zext i1 %arg0 to i8
Expand All @@ -511,9 +502,7 @@ define i8 @commonArgWithXor0(i1 %arg0) {

define i8 @commonArgWithXor1(i1 %arg0) {
; CHECK-LABEL: @commonArgWithXor1(
; CHECK-NEXT: [[V0:%.*]] = zext i1 [[ARG0:%.*]] to i8
; CHECK-NEXT: [[V1:%.*]] = select i1 [[ARG0]], i8 9, i8 1
; CHECK-NEXT: [[V2:%.*]] = xor i8 [[V1]], [[V0]]
; CHECK-NEXT: [[V2:%.*]] = select i1 [[ARG0:%.*]], i8 8, i8 1
; CHECK-NEXT: ret i8 [[V2]]
;
%v0 = zext i1 %arg0 to i8
Expand All @@ -524,10 +513,7 @@ define i8 @commonArgWithXor1(i1 %arg0) {

define i8 @commonArgWithXor2(i1 %arg0) {
; CHECK-LABEL: @commonArgWithXor2(
; CHECK-NEXT: [[V0:%.*]] = zext i1 [[ARG0:%.*]] to i8
; CHECK-NEXT: [[V1:%.*]] = select i1 [[ARG0]], i8 1, i8 7
; CHECK-NEXT: [[V2:%.*]] = xor i8 [[V1]], [[V0]]
; CHECK-NEXT: [[V3:%.*]] = or disjoint i8 [[V2]], 16
; CHECK-NEXT: [[V3:%.*]] = select i1 [[ARG0:%.*]], i8 16, i8 23
; CHECK-NEXT: ret i8 [[V3]]
;
%v0 = zext i1 %arg0 to i8
Expand All @@ -539,10 +525,7 @@ define i8 @commonArgWithXor2(i1 %arg0) {

define i8 @commonArgWithXor3(i1 %arg0) {
; CHECK-LABEL: @commonArgWithXor3(
; CHECK-NEXT: [[V0:%.*]] = zext i1 [[ARG0:%.*]] to i8
; CHECK-NEXT: [[V1:%.*]] = select i1 [[ARG0]], i8 5, i8 45
; CHECK-NEXT: [[V2:%.*]] = xor i8 [[V1]], [[V0]]
; CHECK-NEXT: [[V3:%.*]] = or disjoint i8 [[V2]], 16
; CHECK-NEXT: [[V3:%.*]] = select i1 [[ARG0:%.*]], i8 20, i8 61
; CHECK-NEXT: ret i8 [[V3]]
;
%v0 = zext i1 %arg0 to i8
Expand Down